A Swiss man seeking to travel to the Syrian town of Idlib with a load of weapons was arrested at the Bulgarian-Turkish border and charged with "terrorism", the Bulgarian prosecutor announced on Thursday.

The man was arrested Tuesday evening at the Kapitan-Andrevo border post in a 4x4 vehicle in which three rifles, a pistol, some 400 cartridges and 24 knives were found, as well as an itinerary leading to Idlib, a rebel stronghold in northwest Syria increasingly targeted by the Damascus regime.

The United Nations and relief organisations fear that a major assault in Idlib, which borders Turkey, could spark one of the worst humanitarian disasters of the Syrian conflict to date.

The Swiss national explained that he wanted to help "civilians" in Syria.

The suspect had been flagged by the Swiss authorities, to whom his father had reported his disappearance. He has been charged with terrorism and weapons smuggling.

Bulgaria is located on one of the main land routes used by suspected combatants seeking to travel to or from Syria. Arrests are declining after peaking in 2015, at the height of the activities of the Islamic State group.

AFP/ds